In recent years, an optical image measuring technique of scanning a measured object with light beam from a laser light source etc. and forming images that show the surface morphology and internal morphology of measured objects has attracted attention. Unlike an X-ray CT apparatus, the optical image measuring technique is noninvasive to human bodies, and is therefore expected to be utilized particularly in the medical field.
As examples of such an optical image measurement device, there are an OCT (Optical Coherence Tomography) device and a scanning laser ophthalmoscope (SLO) used in ophthalmology. The SLO is a device that projects laser light into an eyeball with high speed scan, detects a reflected light from a fundus oculi by a high sensitive light detection element, and forms an image. Below, the OCT device is particularly described as an example of the optical image measurement device.
Japanese Unexamined Patent Application Publication No. Hei 11-325849 discloses an example of the optical image measuring technique. This device has such a configuration that: a measuring arm scans an object by a rotary deflection mirror (a galvanomirror); a reference arm is provided with a reference mirror; and an interferometer is mounted at the outlet to analyze, by a spectrometer, the intensity of an interference light of light fluxes from the measurement arm and the reference arm; the reference arm is provided with a device that gradually changes the light flux phase of the reference light by discontinuous values.
The optical image measurement device in Japanese Unexamined Patent Application Publication No. Hei 11-325849 uses a technique of so-called “Fourier Domain OCT (Optical Coherence Tomography).” That is to say, the device radiates a low-coherence light beam to a measured object, acquires the spectral intensity distribution of interference light of the reflected light and the reference light, and executes Fourier transform, thereby imaging the morphology in the depth direction (the z-direction) of the measured object.
Furthermore, the optical image measurement device described in Japanese Unexamined Patent Application Publication No. Hei 11-325849 is provided with a galvanomirror that scans with a light beam (a signal light), and is thereby configured to form an image of a desired measurement target region of the measured object. Because this device is configured to scan with the light beam only in one direction (the x-direction) orthogonal to the z-direction, an image formed by this device is a two-dimensional tomographic image in the depth direction (the z-direction) along the scanning direction (the x-direction) of the light beam.
Japanese Unexamined Patent Application Publication No. 2002-139421 discloses a technique of scanning with a signal light in the scanning direction (the x-direction) and the vertical direction (the y-direction that is perpendicular to both the x-direction and the z-direction) to form a plurality of two-dimensional tomographic images in the scanning direction (the x-direction), and acquiring and imaging three-dimensional tomographic information of a measured range based on the tomographic images. As the three-dimensional imaging, for example, a method of arranging and displaying a plurality of tomographic images in the vertical direction (the y-direction) (referred to as stack data or the like), and a method of executing a rendering process on a plurality of tomographic images to form a three-dimensional image are considered.
Japanese Unexamined Patent Application Publication No. 2007-24677 describes, as an example of other types of optical image measurement devices, an optical image measurement device that images the morphology of a measured object by scanning the measured object with light of various wavelengths, acquiring the spectral intensity distribution based on an interference light obtained by superposing the reflected lights of the light of the respective wavelengths on the reference light, and executing Fourier transform. Such an optical image measurement device is called a Swept Source type or the like.